Let’s Get Passive About Energy Efficiency

On last week’s Energy Efficiency Industry Cluster Tour, one of our stops was a green building project designed by Mithun, a local architecture firm. In describing the building’s energy efficiency feature, our guide used the analogy of buildings as “either sailboats or powerboats.” I thought it was a great analogy, and really highlighted that, sometimes, the best way to ensure energy efficiency in a building is to do nothing.

Of course, by nothing, I mean a lot. In the analogy, there are two pays to power your boat. If you want a sailboat, you think a lot about design, materials and construction to build something that is mainly powered by the elements. If you want a powerboat, you think about getting the best equipment. Applied to buildings, energy efficiency through the powerboat approach is to install smart HVAC systems, smart meters and high tech lighting. Essentially, it’s using high tech solutions to reduce electricity usage, which are the kinds of products that BETI is focused on testing and commercializing.

The sailboat approach is all about things like using windows, insulation and design to to maximize natural light and temperature. Taken to its most extreme, the best sailboat is the “passive house,” which has been in the news quite a bit recently:

Where possible, passive construction maximizes window and facade exposures toward the southern sun. Thick walls and abundant insulation are also cornerstones of the process. Walls in a typical American home might be about six inches thick and insulated with fiberglass batting. The walls of the Landaus’ new home are nearly three times as thick — a citadel of insulation and tape-sealed construction intended to keep the cold at bay and to prevent costly heat from slithering out through cracks, holes and other imperfections common to conventional construction. And more than a foot of rigid foam insulation sits between the earth and the concrete slab forming the Landaus’ basement. Fresh air is continuously pulled into the house, and stale air pushed out through a sophisticated mechanical ventilation system that can serve double-duty as a heat saver: some of the thermal energy being carried by the exhaust air is transferred to the intake air, minimizing heat loss. As for preventing pipes from freezing, the Landaus will rely on two heat sources — a wood-burning stove on the main floor and electric radiant floors in the bathrooms. When the house is occupied, the wood-burning stove is capable of heating the whole house. When no one is home, the electric radiant floors can maintain a minimum temperature throughout the house to avoid plumbing disasters. To heat water, the family will depend on solar thermal collectors on the roof.

Of course, the problem with the passive house approach is that a lot of buildings are already built, and so retrofit through “powerboat” technology is still a major factor in reducing energy consumption. But it’s interesting to see energy efficiency as a whole get increasing attention, and to think about how both kinds of boats can be part of the energy efficiency fleet.

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